Dimensional reduction by pressure in the magnetic framework material CuF$_{2}$(D$_{2}$O)$_{2}$pyz: from spin-wave to spinon excitations

TL;DR

This study demonstrates how applying high pressure to the magnetic framework material CuF$_{2}$(D$_{2}$O)$_{2}$pyz induces a transition from two-dimensional spin-wave excitations to one-dimensional spinon excitations, revealing a magnetic dimensional crossover.

Contribution

We experimentally show pressure-induced magnetic dimensional crossover in CuF$_{2}$(D$_{2}$O)$_{2}$pyz using neutron scattering, highlighting the tunability of magnetic phases in metal-organic magnets.

Findings

Low pressure state exhibits 2D spin-wave excitations.

High pressure state exhibits 1D spinon continuum.

Pressure induces a transition from 2D to 1D magnetic behavior.

Abstract

Metal organic magnets have enormous potential to host a variety of electronic and magnetic phases that originate from a strong interplay between the spin, orbital and lattice degrees of freedom. We control this interplay in the quantum magnet CuF$_2$(D$_2$O)$_2$pyz by using high pressure to drive the system through a structural and magnetic phase transition. Using neutron scattering, we show that the low pressure state, which hosts a two-dimensional square lattice with spin-wave excitations and a dominant exchange coupling of 0.89 meV, transforms at high pressure into a one-dimensional spin-chain hallmarked by a spinon continuum and a reduced exchange interaction of 0.43 meV. This direct microscopic observation of a magnetic dimensional crossover as a function of pressure opens up new possibilities for studying the evolution of fractionalised excitations in low dimensional quantum magnets and eventually pressure-controlled metal--insulator transitions.